A hybrid vehicle having an internal combustion engine and an electric motor as power sources includes a vehicle having a power supply system in which a voltage converting device boosts a low output voltage of a power storage device and supplies the boosted high-voltage electric power to a motor for driving. Japanese Patent Laying-Open No. 2003-209969 (Patent Document 1), for example, discloses a technique related to power control over such a hybrid vehicle including a plurality of units each having the power storage device and the voltage converting device.
A power supply control system disclosed in Japanese Patent Laying-Open No. 2003-209969 includes: an inverter for converting DC power to AC power and supplying the AC power to an electric traction motor; a plurality of power supply stages for providing DC power to the inverter, each stage having a battery and a voltage converting device and the stages being wired in parallel; and a controller for controlling the plurality of power supply stages. The controller controls the plurality of power supply stages such that the batteries of the plurality of power supply stages are equally charged/discharged and the plurality of power supply stages maintain an output voltage to the inverter.